To facilitate evacuation of an elevator car, many elevator systems are deliberately designed so that the car doors can be manually pulled open. With the car doors open, however, the hoistway door latch or interlock (which prevents occupants on the floor from opening the hoistway doors when the car is not safely close to the floor) may be released by the passengers, who can then pull the hoistway doors open. But, if the car is substantially above the floor level when this is done, there is a rather large space, between the bottom of the car and the floor, leading to the shaft or hoistway. Passengers attempting to leave a car which is at that particular position may, inadvertently, step or slip through that space in attempting to reach the floor.
It is not surprising, then, that there is a need for a safety arrangement which, if the car is in an "unsafe zone" (too far above the floor for passengers to reach the floor), prevents passengers from opening the car doors and pulling the hoistway doors back far enough to enable them to exit the car yet allows the doors to be opened, at any car position, from the floor; in other words, a system that allows the passengers to leave only if the car is in a "safe zone" (close to the floor). Obviously, an arrangement meeting these requirements should also allow the passengers to open the car doors enough to communicate with people on the floor and to receive emergency equipment.
U.S. patent application Ser. No. 120,443, by Gibson et al, filed on Feb. 11, 1980, titled BETWEEN LANDING CAR DOOR SAFETY LOCK, now abandoned and also assigned to the owner of this application, shows a system which meets most of these requirements. In that system the car and hoistway doors engage each other in such a way that the hoistway doors, which are closed by the safety interlock, stop the car doors from opening. But, because of that, the car doors cannot be opened without simultaneously opening the hoistway doors. U.S. Pat. No. 1,838,524 shows an arrangement which couples the car and hall door and prevents the car door from opening between landings, but it does not permit limited opening of the car door at certain car positions.